It is known to arrange an exhaust purification catalyst in an engine exhaust passage of an internal combustion engine to remove the carbon monoxide (CO), hydrocarbons (HC), and further nitrogen oxides (NOX) and other components which are contained in the exhaust gas. The exhaust purification catalyst has an activation temperature which enables components of the exhaust gas to be removed at a high efficiency. Right after starting up an internal combustion engine after stopping it for a long time period etc., the exhaust purification catalyst is less than the activation temperature. It is desirable to quickly raise the exhaust purification catalyst to the activation temperature or more.
Japanese Patent Publication No. 11-324765A discloses a direct injection spark ignition type of internal combustion engine which warms up an exhaust purification catalyst in the time period from the time of start-up to when the exhaust purification catalyst is activated. In this internal combustion engine, when controlling the air-fuel ratio of the air-fuel mixture to the stoichoimetric one for combustion, fuel is injected in the intake stroke so as to form a homogeneous air-fuel mixture which is leaner than the stoichiometric one in the combustion chamber as a whole. Further, fuel is injected in the compression stroke so as to form and burn an air-fuel mixture which is relatively richer than the stoichiometric one in a stratified state around the spark plug. This discloses that this internal combustion engine can increase the ratio of CO which is contained in the burned gas and can easily react by an oxidation reaction and can lower the HC ratio. Further, this discloses to set the ignition timing to the retarded side.
Japanese Patent Publication No. 2001-182586A discloses an exhaust temperature raising device which injects an amount of fuel for locally generating a rich air-fuel mixture around a spark plug in a compression stroke when a rise in temperature of the exhaust gas is demanded. The exhaust temperature raising device controls the engine control parameters so that the part of the fuel which is incompletely burned when the fuel is ignited and burned burns by being mixed with the excess oxygen in the cylinder. It discloses that this exhaust temperature raising device controls a fuel injector so that the overall air-fuel ratio in a combustion chamber becomes an air-fuel ratio which is somewhat leaner than the stoichiometric air-fuel ratio.
Japanese Patent Publication No. 2004-124824A discloses an internal combustion engine which is provided with a secondary air feed device wherein the feed of secondary air is prohibited until the temperature of the exhaust port becomes a predetermined temperature or more and thereby the exhaust port is kept from being cooled by the secondary air. Further, this publication discloses that if feeding secondary air immediately after start-up of the internal combustion engine, since the secondary air is low in temperature, the carbon monoxide and hydrocarbons in the exhaust gas do not react by afterburn and the exhaust port ends up being cooled by the low temperature secondary air.